Seafood is enjoying a new place of respect and desirability now that it has been endorsed scientifically as one of the most healthful protein foods for avoiding heart disease.

Health agencies, including the American Heart Assn., now recommend that Americans eat fish frequently (at least two or three times a week according to the AHA), because it contains "omega-3 fatty acid," a highly polyunsaturated fat that helps reduce the risk of cardiovascular disease. These polyunsaturated fats (even more polyunsaturated than margarine) present in fish act as an antifreeze in fish and have much the same blood-thinning effect, preventing clotting, and, thus, hardening of the arteries in humans.

Studies show that adding more fish to the diet causes triglycerides and cholesterol counts to go down. (A 20-year study in Denmark following 850 middle-aged men in 1985 showed that the mortality rate was more than 50% lower among those who ate an average of one ounce of fish per day.

There is just one thing wrong. Most home chefs have problems handling and cooking fish. Education simply is not there for most people raised on meat, and, in many cases, meat alone. Fish, does, indeed, require skill if it is to be properly purchased, handled and cooked.

If the consumer is eating more--and they are--(about 15.4 pounds in 1987 compared with 11.8 pounds in 1970), most of it is being done in restaurants, not in homes, according to a Better Homes and Gardens 1986 survey showing that 65% of the fish-eating public eat seafood outside of the home. Fear of cooking fish and fear of not purchasing the proper quality fish are reasons for the restaurant dining phenomenon.

To help correct the gap, registered dietitian Janis Harsila and Evie Hansen, both wives of fishermen in Washington state, who eat seafood six to seven days a week, came up with "Seafood: A Collection of Heart-Healthy Recipes." The cookbook has, so far, been received with open arms by consumers hungry for information on a food that is good for them. With 45,000 copies sold, the book is considered a nationwide best seller.

The reason is simple. The book addresses itself the educational problems consumers face when dealing with fish.

There are about 150 easy recipes, which require less than 20 minutes per recipe to prepare and are also low in fat and calories. More than 35 species of fish and shellfish are discussed in the book.

There also are tips for selecting, handling and preparing all seafood--both shellfish and fish--in its various forms, as fillets, steaks and whole fish.

Hansen, one of the authors, stopped by at The Times during her last book tour to discuss some of the problems most consumers have with fish.

"If people knew how much they could enjoy fresh seafood as fresh as we get it, they would be eating fish seven days a week the way we are," she said.

Actually, according to Hansen, fresh-frozen fish is as good as "fresh as we get it," because it is frozen within two to three hours from the time caught. "People have a misconception that frozen fish is not fresh. Actually it is far more fresh than so-called fresh fish you buy at the fish counter where it may have stood under refrigeration for weeks, just as is done with fresh produce," she said.

Many fishermen today start out making frozen fish their goal as soon as the fish is caught. "If that is their goal, you can be sure that within a few minutes, the fish is bled, gutted, filleted and frozen whole within two or three hours. The fish is then kept at minus 20 degrees, which seals in every fresh quality with no chance of deterioration or nutrient loss," said Hansen.

Fresh fish kept iced at 32 degrees from the moment caught until it reaches the supermarket shelf would still be considered fresh for 21 days thereafter, according to University of Washington research, Hansen pointed out. Research reported in two separate retail trade publications (Seafood Leader and Seafood Business Report) indicates that flash-frozen fish won out over fresh fish in a test on ultimate freshness.

"If people knew they could have good fish whether fresh or frozen, they would eat more fish," Hansen said.

To purchase fish with confidence, you have to know what you are looking for, claims Hansen. "One should feel as confident when shopping for fish as when shopping for corn."

But is one?

According to Hansen, if you are buying frozen fish, look for a label that says "frozen at sea," indicating that a factory trawler or small boat with freezing equipment on board has caught and frozen the fish within hours if not minutes.

If you purchase fresh fillets, steaks or roasts that have been thawed or are fresh, look for bright, clean, good color. If you are allowed to touch the fish, the flesh should be firm. Fish should not have any offensive odor, except for a whiff of fresh ocean breezes, if at all. If the odor is even slightly offensive, don't buy it.